Golang encoding.DecodeStringAscending函数代码示例

func (p *planner) getTableNames(dbDesc *DatabaseDescriptor) (parser.QualifiedNames, *roachpb.Error) {
	prefix := MakeNameMetadataKey(dbDesc.ID, "")
	sr, pErr := p.txn.Scan(prefix, prefix.PrefixEnd(), 0)
	if pErr != nil {
		return nil, pErr
	}

	var qualifiedNames parser.QualifiedNames
	for _, row := range sr {
		_, tableName, err := encoding.DecodeStringAscending(
			bytes.TrimPrefix(row.Key, prefix), nil)
		if err != nil {
			return nil, roachpb.NewError(err)
		}
		qname := &parser.QualifiedName{
			Base:     parser.Name(dbDesc.Name),
			Indirect: parser.Indirection{parser.NameIndirection(tableName)},
		}
		if err := qname.NormalizeTableName(""); err != nil {
			return nil, roachpb.NewError(err)
		}
		qualifiedNames = append(qualifiedNames, qname)
	}
	return qualifiedNames, nil
}

func decodeKeyPrint(key roachpb.Key) string {
	var buf bytes.Buffer
	for k := 0; len(key) > 0; k++ {
		var err error
		switch encoding.PeekType(key) {
		case encoding.Null:
			key, _ = encoding.DecodeIfNull(key)
			fmt.Fprintf(&buf, "/NULL")
		case encoding.NotNull:
			key, _ = encoding.DecodeIfNotNull(key)
			fmt.Fprintf(&buf, "/#")
		case encoding.Int:
			var i int64
			key, i, err = encoding.DecodeVarintAscending(key)
			if err == nil {
				fmt.Fprintf(&buf, "/%d", i)
			}
		case encoding.Float:
			var f float64
			key, f, err = encoding.DecodeFloatAscending(key, nil)
			if err == nil {
				fmt.Fprintf(&buf, "/%f", f)
			}
		case encoding.Bytes:
			var s string
			key, s, err = encoding.DecodeStringAscending(key, nil)
			if err == nil {
				fmt.Fprintf(&buf, "/%q", s)
			}
		case encoding.BytesDesc:
			var s string
			key, s, err = encoding.DecodeStringDescending(key, nil)
			if err == nil {
				fmt.Fprintf(&buf, "/%q", s)
			}
		case encoding.Time:
			var t time.Time
			key, t, err = encoding.DecodeTimeAscending(key)
			if err == nil {
				fmt.Fprintf(&buf, "/%s", t.UTC().Format(time.UnixDate))
			}
		case encoding.TimeDesc:
			var t time.Time
			key, t, err = encoding.DecodeTimeDescending(key)
			if err == nil {
				fmt.Fprintf(&buf, "/%s", t.UTC().Format(time.UnixDate))
			}
		default:
			// This shouldn't ever happen, but if it does let the loop exit.
			fmt.Fprintf(&buf, "/%q", []byte(key))
			key = nil
		}

		if err != nil {
			fmt.Fprintf(&buf, "/<%v>", err)
			continue
		}
	}
	return buf.String()
}

// ShowDatabases returns all the databases.
// Privileges: None.
//   Notes: postgres does not have a "show databases"
//          mysql has a "SHOW DATABASES" permission, but we have no system-level permissions.
func (p *planner) ShowDatabases(n *parser.ShowDatabases) (planNode, *roachpb.Error) {
	// TODO(pmattis): This could be implemented as:
	//
	//   SELECT id FROM system.namespace WHERE parentID = 0

	prefix := MakeNameMetadataKey(keys.RootNamespaceID, "")
	sr, pErr := p.txn.Scan(prefix, prefix.PrefixEnd(), 0)
	if pErr != nil {
		return nil, pErr
	}
	v := &valuesNode{columns: []column{{name: "Database", typ: parser.DummyString}}}
	for _, row := range sr {
		_, name, err := encoding.DecodeStringAscending(
			bytes.TrimPrefix(row.Key, prefix), nil)
		if err != nil {
			return nil, roachpb.NewError(err)
		}
		v.rows = append(v.rows, []parser.Datum{parser.DString(name)})
	}
	return v, nil
}

func decodeTableKey(valType parser.Datum, key []byte, dir encoding.Direction) (
	parser.Datum, []byte, error) {
	if (dir != encoding.Ascending) && (dir != encoding.Descending) {
		return nil, nil, util.Errorf("invalid direction: %d", dir)
	}
	var isNull bool
	if key, isNull = encoding.DecodeIfNull(key); isNull {
		return parser.DNull, key, nil
	}
	var rkey []byte
	var err error
	switch valType.(type) {
	case parser.DBool:
		var i int64
		if dir == encoding.Ascending {
			rkey, i, err = encoding.DecodeVarintAscending(key)
		} else {
			rkey, i, err = encoding.DecodeVarintDescending(key)
		}
		return parser.DBool(i != 0), rkey, err
	case parser.DInt:
		var i int64
		if dir == encoding.Ascending {
			rkey, i, err = encoding.DecodeVarintAscending(key)
		} else {
			rkey, i, err = encoding.DecodeVarintDescending(key)
		}
		return parser.DInt(i), rkey, err
	case parser.DFloat:
		var f float64
		if dir == encoding.Ascending {
			rkey, f, err = encoding.DecodeFloatAscending(key, nil)
		} else {
			rkey, f, err = encoding.DecodeFloatDescending(key, nil)
		}
		return parser.DFloat(f), rkey, err
	case *parser.DDecimal:
		var d *inf.Dec
		if dir == encoding.Ascending {
			rkey, d, err = encoding.DecodeDecimalAscending(key, nil)
		} else {
			rkey, d, err = encoding.DecodeDecimalDescending(key, nil)
		}
		dd := &parser.DDecimal{}
		dd.Set(d)
		return dd, rkey, err
	case parser.DString:
		var r string
		if dir == encoding.Ascending {
			rkey, r, err = encoding.DecodeStringAscending(key, nil)
		} else {
			rkey, r, err = encoding.DecodeStringDescending(key, nil)
		}
		return parser.DString(r), rkey, err
	case parser.DBytes:
		var r []byte
		if dir == encoding.Ascending {
			rkey, r, err = encoding.DecodeBytesAscending(key, nil)
		} else {
			rkey, r, err = encoding.DecodeBytesDescending(key, nil)
		}
		return parser.DBytes(r), rkey, err
	case parser.DDate:
		var t int64
		if dir == encoding.Ascending {
			rkey, t, err = encoding.DecodeVarintAscending(key)
		} else {
			rkey, t, err = encoding.DecodeVarintDescending(key)
		}
		return parser.DDate(t), rkey, err
	case parser.DTimestamp:
		var t time.Time
		if dir == encoding.Ascending {
			rkey, t, err = encoding.DecodeTimeAscending(key)
		} else {
			rkey, t, err = encoding.DecodeTimeDescending(key)
		}
		return parser.DTimestamp{Time: t}, rkey, err
	case parser.DInterval:
		var d int64
		if dir == encoding.Ascending {
			rkey, d, err = encoding.DecodeVarintAscending(key)
		} else {
			rkey, d, err = encoding.DecodeVarintDescending(key)
		}
		return parser.DInterval{Duration: time.Duration(d)}, rkey, err
	default:
		return nil, nil, util.Errorf("TODO(pmattis): decoded index key: %s", valType.Type())
	}
}